To read and/or write data from/on a disk such as a DVD by using light that has been emitted from a laser diode or any other light source, the operation of a disk drive needs to be controlled such that the point of convergence (i.e., the focal point) of the light is always located right on the information storage layer of the disk. This type of control is called a “focus control”. To realize the focus control, an objective lens in an optical pickup is arranged near the disk.
However, since the objective lens is located close to the disk, the objective lens might contact with, or collide against, the disk loaded or a member of the disk drive while no focus control is being performed.
Thus, a technique of avoiding such a collision is needed. For example, Patent Document No. 1 discloses a technique of avoiding a collision between an objective lens and the cartridge of a disk being inserted into, or removed from, a disk drive. Hereinafter, it will be described with reference to FIGS. 1 and 2 how such a conventional disk drive works for that purpose.
FIG. 1 shows a configuration for a conventional disk drive 100. A disk 101 is stored in a cartridge 102 and has an information storage layer L. An optical pickup 103 includes an objective lens 123 and an actuator 122 for driving the objective lens 123 and detects the light that has been reflected from the information storage layer L of the disk 101. A focus error signal generating circuit 112 generates a focus error signal, representing how much the focal point of the light has shifted from the information storage layer L, based on the output of the optical pickup 103. In response to the output of the focus error signal generating circuit 112, a focus control circuit 120 outputs a focus control signal to get the focal point located right on the information storage layer L. An actuator driver circuit 121 drives the actuator 122 responsive to a drive control signal e, thereby moving the objective lens 123 perpendicularly to the information storage layer L.
An energizing signal generator 135 outputs a signal that moves the objective lens away from the disk 101 by energizing the actuator 122. In accordance with an instruction given by a system controller 130, a switching circuit 131 switches the output of the focus control circuit 120 into that of the energizing signal generator 135, or vice versa, and supplies the selected output signal to the actuator driver circuit 121. The output of a sensor that senses the insertion of the disk 101 and the output of an eject button for removing the disk 101 are connected to the system controller 130.
FIG. 2 shows the waveforms of internal signals in the conventional disk drive 100 to get a lens retracting operation done.
When the sensor (not shown) senses the insertion of the disk 101 that has been stored in the cartridge 102 but has just started being loaded, the system controller 130 instructs the switching circuit 131 to pass the output of the energizing signal generator 135 to the actuator driver circuit 121. When current begins to flow through the actuator 122, the objective lens 123 moves away from the disk 101. If the disk 101 starts being loaded in such a state, then the objective lens 123 will not collide against the cartridge 102 and the disk 101 can be loaded safely. Thereafter, when the switching circuit 131 shuts off the output of the energizing signal generator 135, the actuator 122 goes back to its original position.
Similar operations are carried out when the disk is unloaded. Specifically, when the eject button (not shown) is pressed, the system controller 130 receives its output. Then, the system controller 130 instructs the switching circuit 131 to pass the output of the energizing signal generator 135 to the actuator driver circuit 121. When current begins to flow through the actuator 122, the objective lens 123 moves away from the disk 101. If the disk 101 starts being unloaded in such a state, then the objective lens 123 will not collide against the cartridge 102 and the disk 101 can be unloaded safely. Thereafter, when the switching circuit 131 shuts off the output of the energizing signal generator 135, the actuator 122 goes back to its initial position.                Patent Document No. 1: Japanese Patent Application Laid-Open Publication No. 4-141830 (see page 1 and FIG. 1, in particular)        